The relative explosion in the popularity of gift cards around the country has led to a number of different secondary markets for cards consumers want to sell.

According to one, CardHub.com, consumers purchased almost $28 million in gift cards over the 2011 holiday season and an estimated $41 billion in gift card balances have gone unredeemed since 2005.

This has created a secondary market for gift cards among consumers that want to buy and sell them. CardHub claims to be the only gift card exchange in the nation that allows consumers to sell or swap any gift card regardless of brand or store affiliation.

While many people simply don't know that you can sell unwanted gift cards online for cash, others are discouraged from doing because their card is not affiliated with a major national retailer and therefore will not be accepted by an online gift card exchange.

Or they used some of the card's funds and an unusual denomination remains. Or they have store credit instead of an actual gift card or they don't want to give up any value to middle men, explained CardHub CEO Odysseas Papadimitriou.

Papadimitriou said people might also want to re-gift them, swap them, sell them to pay down debt or donate them to charity.

“According to Card Hub's latest study, U.S. consumers were projected to end 2011 with roughly $64 billion more credit card debt than they began it with.  Every little bit counts when it comes to paying down what we owe, which means that the $41 billion that U.S. households have in unused gift cards would sure come in handy,” Papadimitriou added.